Radiofrequency transformer



H. K. SANDELL mmxo FREQUENCY nmsxoun June 9, 1925. 1,541,398

Filed Inch 5, 1923 III" lllllllul nunummmm will T iIIH E222" 2.623472%?22, i .9 f 1/3 5 Patented June 9, 1925.

UNITED STATES HENRY K. SANDELL, OF CHICAGO, ILLINOIS.

RADIOEREQUENCY TRANSFORMER.

Application filed March 5, 1923. Serial No. 622,87

To all whom it may concern:

Be it known that I, HENRY K. SANDELL, a citizen of theUnited States, residing at Chicago, in the county of Cook'and State of Illinois, have invented a new and useful Improvement in Radiofrequency Transformers, of which the following is a specification.

This invention relates to radio frequency transformer and the like, and is particularly adapted to be used for radio frequency amplification in radio receiving sets.

The invention is fully described in the following specification and shown in the accompanying drawings in which:

Figure 1 is an enlarged side elevation of an embodiment of the invention.

Fig. 2 is a partial vertical section through the transformer on the line 2 of Fig. 3;

Fig. 3 is a horizontal section on the line 3 of Fig. 2 and Fig. 4 is a side elevation of the primary coil showing the soft iron wires of the core as before being bent around the secondary.

The embodiment illustrated comprises a primary coil 10 wound about a tube 11 of insulating material in which is placed a series of wires 12 consisting of very soft iron.

Over the primary coil 10 is placed a spool 13 of insulating material having a series of annular compartments or grooves 14 therein in each of which is wound a number of turns of wire forming a secondary coil 15. This winding is accomplished by starting at one end of the spool, winding the desired number of turns in the first groove carrying the wire through a slot (not shown) to the next groove, winding that, and proceeding through each succeeding groove to the opposite end.

With the secondary winding placed over the primary winding the wires 12 are then bent around thesecondary so that their ends overlap. These ends are then secured in any desired manner, and these windings are enclosed within a housing 16, the two ends of the primary winding being carried to binding posts 17 and 18, and the two ends of the secondary to binding posts 19 and 20 in the base 21 whereby the transformer may be readily inserted into a radio receiving set.

A supporting bracket 22 preferably of insulating material is secured to the housing 16 and has an adjusting screw 23 threaded therein.

the movable core 26. Thus the primary is aperiodic and the secondary is periodic or resonant for the present broadcasting range.

With this arrangement the transformer is very delicate, the response obtainable being varied by raising and lowering the wires 26 of the movable core.

By raising and lowering the movable core the desaturation time of the iron is varied, and by properly choosing the values, this time may be brought into step or resonance with the natural period of inductance of the secondary coil. In other words, varying the iron in the core varies the frequency of the secondary coil so that by this means, the resonance of the circuit in which the secondary coil is placed may be tuned.

When this occurs, the strength of current flowing in this coil is greatly increased. The relation between the soft iron core and the secondary is very sensitive to small changes in either, while relatively large changes in the primary are permissible without materially altering the operation of the transformer.

If desired short pieces of the soft iron wire may be embedded in a non-magnetic substance to form the movable core and by properly proportioning this, the wires 12.

may be omitted altogether.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims, in which it is my intention to claim all novelty inherent in my invention as broadly asv possible-in view of the prior. art.

What I regard as new and desire to secure by Letters Patent, is:

1. A radio-frequency transformer comprising an aperiodic primary winding, a secondary winding periodic to the frequencies of the band of waves it is desired to receive, said windings being substantially coaxial, a fixed soft iron core and a soft iron core movable into and out of inductive relation to said windings, whereby the frequency of the circuit in which the secondary winding is placed may be tuned.

2. A radio-frequency transformer comprising an aperiodic primary winding, a periodic secondary winding, said windings being substantially coaxial, a fixed soft iron coreconsisting of a plurality of small soft iron wires, and a soft iron core movable into and out of inductive relation to said windings, whereby the frequency of the circuit in which the secondary winding is placed may be tuned.

3. A radio-frequency transformer comprising an' aperiodic primary Winding, a periodic secondary winding, said windings being substantially coaxial, a fixed soft iron core consisting of a plurality of small soft iron wires, the ends of each wire passing around said windings and being brought into substantially overlapping position, and a soft iron core movable into and out of inductive relation to said windings, whereby the frequency of the circuit in which the secondary winding is placed may be tuned.

4. A radio-frequency transformer comprising an aperiodic primary winding, a periodic secondary winding, said windings being substantially coaxial, a fixed soft iron core, and a core of soft iron wires movable into and out of inductive relation to said windings, whereby the frequency of the circuit in which the secondary winding is placed may be tuned.

5. In combination, a winding having a natural frequency within the radio range, a fixed soft iron core, and a magnetic core movable therein for varying the frequency of said winding.

HENRY K. SAN DELL. 

